The present invention relates to a vibrating motor used as a vibration messaging device employed largely in portable apparatuses.
Cellular phones, among other portable apparatus, are desired to be easy-to-carry, operable for long hours and having superior functions. Naturally, the motor to be mounted to the cellular phones is required to meet those requirements. To be more specific, the motor should be firstly of small size and lightweight, and secondly, produce the maximum vibrations at low power consumption.
A coreless motor in a cylinder having a small diameter has been used because it more or less meets those requirements. U.S. Pat. No. 5,621,260 (based on Japanese Patent Non-examined Application Publication Nos. H04-268507, H05-5561 and H05-115720) has also been obtained based on this technique.
This prior art teaches the following technique: a low-magnetic-flux-density section in a yoke through which magnetic flow travels is specified, and the thickness of the section is reduced so that the motor can maintain its performance although its outer dimensions are lessened. Such techniques have been accumulated thereby dealing with demands from the market.
Recently a number of cellular phones producing enough vibrations has increased, and when the cellular phone put on a desk produces vibrations, the phone moves on the desk due to the vibrations and falls thereoff. Since this kind of accident occur so frequently, this moving phenomenon should be avoided and yet a large vibrating message is desirably produced in addition to satisfying the requirements discussed above. This moving phenomenon is influenced by a rotary shaft of the motor because the rotary shaft is disposed parallel to the desktop surface. This parallel rotary shaft often imparts a force of moving the cellular phone parallel with the desk-top when the phone receives a force of taking off the desk-top by rotating an unbalancing weight. A countermeasure against this moving phenomenon is to dispose the rotary shaft in a manner other than parallel with the desk-top. In other words, a flat and thin motor having a rotary shaft vertical with regard to the desktop is desired.
In order to enhance the easy-to-carry characteristic of cellular phones without losing the easy-to-operate feature, a thinner body is desired from the market. The vibrating motor is thus desirably in the thinner structure. The vibrating motor desirably addresses this third issue in addition to the two issues discussed above, i.e. the first one is small size and lightweight, the second one is to produce the maximum vibrations at low power consumption.
The thin vibrating motor, desired thirdly, has been disclosed in U.S. Pat. No. 4,980,590 (based on Japanese Patent Non-examined Application Publication No. S62-246383.) This prior art teaches a flat brushless vibrating motor. This prior art employs a coreless motor having an axial air-gap type magnetic field and a rotary-back-yoke so that a compact size vibrating motor without disposing an unbalancing weight on an output shaft can be realized. The rotary-back-yoke is formed in an unbalanced shape thereby building a vibration-producing-function in the motor.
U.S. Pat. No. 5,027,025 has been obtained based on Japanese Patent Non-examined Application Publication No. H01-29114. This prior art further develops its technique discussed above and discloses that an unbalance-producing-function is provided to a rotating magnet of the coreless motor having the axial air-gap type magnetic field. As a result, the greater vibration is producible.
The present invention provides a vibrating motor that is small, lightweight, and provides maximum vibrations at low power consumption, and has a thin and flat structure. The motor has yet a high reliability. A motor of the present invention comprises the following elements:
(a) a stator having a stator core on which coils are wound;
(b) a rotor having a magnet facing the stator core via an annular space, and having a yoke disposed on an outer wall of the magnet; and
(c) an unbalancing weight disposed on an outer wall of the yoke.
This structure allows the motor to satisfy all the requirements, i.e. the small size, light weight, the maximum vibrations at low power consumption, and a thin and flat construction, and yet this structure ensures high reliability. As a result, a thin and flat portable device operable for long hours is achievable.